How to traverse HashMap in Java

　　One.

HASHMAP staff = new HashMap ();

Add keyword value pairs, write your own traversal

Set entries = Staff.entryset ();

Iterator iter = Entries.iterator ();

while (Iter.hasnext ())

{

Map.entry Entry = (map.entry) iter.next ();

Object key = Entry.getkey (); Key words

Object value = Entry.getvalue ();

}

　　Two.

Map map = new HashMap ();

for (Iterator iter = Map.entryset (). iterator (); Iter.hasnext ();) {

Map.entry Entry = (map.entry) iter.next (); Map.entry to remove key values simultaneously

Object key = Entry.getkey ();

Object val = Entry.getvalue ();

}

　　Three.

Map map = new HashMap ();

for (Iterator iter = Map.keyset (). iterator (); Iter.hasnext ();) {

Object key = Iter.next ();

Object val = map.get (key);

}

　　Iterator is an iterator

For the keyset is actually traversed 2 times, one is to iterator, once from the HashMap out of the value of the key.

And EntrySet just traversed the first time, he put the key and value are placed in the entry, so fast.

For us to do the web, may not be part of the Vo object or form to encapsulate information, so when you use HashMap, it is stored in the above objects. Therefore, the use of EntrySet traversal performance will improve.

HashMap use a lot, such as importing information to use, because most of the imported information to determine whether there is duplicate information, so you can use ContainsKey to deal with, and do not have to do when inserting the processing.